Drillable well liner



April 18, 1939- E. B. HALL ET A1.

- DRILLABLE WELL LINER 2 Sheets-Sheet l Filed Jan. 18, 1938 April 18, 1939. E, B. HALL ET A1. 2,155,129

DRILLABLE WELL LINER Filed Jan. '18, 19:58 2 sheets-sheet 2 .Ji-ZG. ff

- Patented Apr. 18, 1939" UNITED STATES PATENT OFFICE IAB Angeles. Calif.

lAppinmnm January 1s. 193s, serial No. 185.530

13Cldms.

This invention relates to a readily drillable liner for use in oil wells and the like, and to a method of placing oil wells on production by the installation of a readily drillable liner so that in this 5 manner precautionary measures are taken to facilitate removal of the liner in the event of subsequent changes of conditions of the well requiring its removal.

By installing a readily drillable liner in a well the liner may be drilled up by conventional drilling equipment of the same general type as that used for drilling through earth formations.

In one sense the invention may be considered as an improvement .or a further development of l5 that which is disclosed in our prior United States Letters Patent No. 2,043,225 issued June 9, 1936. In that patent we have disclosed a method of testing the production of oil-bearing formations wherein a frangible or friable liner is used which may be of such materials as cast metal, cementitious material, ceramic material, glass, Bakelite. or any other impervious material that is readily fractured or broken. 'I'he use of such materials is satisfactory in making a production or formation test but their use is undesirable in a production liner. Formation or production tests made with the method and apparatus disclosed in our prior patent are usually of relatively short duration. Also, the length of the liner is usually relatively short. In making formation or production tests the size of perforations used in the liner is generally regarded as somewhat immaterial particularly when the test is relatively short. In

setting a production liner in oil wells, on the other hand Where the liner is to remain in the well for an indenite period of time, it is important that the liner possesses the property of ductility rather than friability or frangibility. This is because many oil producing formations are subject to violent shifts. The liner, therefore, should be ductile and possess a considerable degree of flexibility so that it will not break or crack when subjected to such formation shifts. l

Friable or frangible materials are not suitable for long production liners since they will not a1- low compressive tensile, or bending forces to be applied thereto Without danger of breakage. It

is not an infrequent occurrence that the walls of the drilled Well sluff or bridge overbefore the 50 installation of the liner and when the liner on being lowered into the well encounters such construction there is a temptation to attempt to force the liner` through these tight locations. If

the liner will not be forced, an attempt is then 55 made to pull the liner loose. IA friable liner is incapable of withstanding such forcing and pulling strains and cannot withstand the abuse to which a production liner is expected to withstand.

so It also happens that while a well is under production that there ,is a settling of sand, silt,`or debris around the liner and this may in the course of time result in forces being applied to the liner tending to crack or break it if it is not ductile. 'I'he danger of such settling occurring during a formation test is seldom present because of the short duration of the test. g

It is now regarded as good practice in setting production liners in oil wells to ascertain the average size of the grains which form the productive formation and to form the perforations'in the liner so that their widths will be approximately twice the diameter of the average grain-size. A liner which possesses the property of ductility lends itself readily to cutting perforations of the desired size with relation to the grain size. Liners that are friable or frangible render this practice impractical due 'to the danger of cracking or breaking the liner in the cutting of the perforations and in chipping the liner around the edges of the perforations. For the foregoing and other reasons, a friable or frangible liner may be satisfactorily employed in formation testing wherein the test is of relatively short duration but they are unsuitable for use as production liners wherein the liner is apt to be much longer and should have the perforations formed with widths conforming to the average grain size and formation. They are also unsuitable where the liner is to be left in the well for an indeterminate length of time and be subjected to formationshifts andthe settling of sand and silt thereabout. i It is; therefore, an object of the present invention to provide a liner for use in oil wells and the like, which will be ductile and which will possess the requisite .property of elasticity or flexibility.

It is another object of the invention to provide a production liner for oil wells and the like which will be adequately strong in tension, compression, and shear so that it may be pulled bodily from the well when occasion requires that the liner be removed and pulling of the liner is possible. 'I'he liner also is to be adequately strong so as to resist collapse.

'I'he present invention contemplates the use of a liner possessing the above-mentioned characteristics which at the Sametime possesses certain physical properties so that it can be readily drilled up by conventional well drilling equipment of the same general type as that used to drill through formations. In this manner, if conditions of the well change after the liner has been installed for a long period of time and the change of conditions requires that the liner be removed either for deepening the well, directional drilling, reconditioning, or rejuvenating the oil sands, the liner can be drilled up and removed. The advantages of such a liner as compared with a well liner heretofore generally employed will be obvious to anyone skilled inthe art..

Where steel liners are employed and the well conditions change requiring either deepening of the well or a scraping of the well walls, or other reconditioning operations, the ability to perform such operations is somewhat dependent upon the ability to pull out the steel liner. When the liner has remained in the well a considerable period of time it is apt to become frozenor immovably lodged therein so that it cannot be pulled. The result is that the liner must either be sidetracked or under favorable conditions it may be milled up by specially designed steel milling and cutting equipment. 'I'here are conditions, however, where even milling of the liner cannot be satisfactorily accomplished. Where it can be accomplished the operation is usually a long and tedious one. By use of the present liner, in the event that the liner becomes lodged in the well so that it cannot be pulled out, the liner may be drilled up by the use of conventional rotary drilling equipment of the type used for drilling through formations. Furthermore, this can be accomplished at a relatively fast rate comparing favorably with the rate at which the formation can be drilled through by the same or similar drilling tools.

It is another object of the invention to provide a drillable liner which will possess the properties of ductility, strength, and malleability and which will have a comparatively low specific gravity so that when occasion requires that the liner be drilled up the cuttings of the liner may be flushed out of the well by the conventional circulation fluid, and will not be left in the bottom of the well hole to interfere with further operations as is the case with steel cuttings when steel liners are milled up.

Still another object of the invention is to provide a liner having the above-mentioned desirable characteristics and which will effectively resist corrosion of such substances as are usually encountered in oil wells so that the liner, even though left in the Well for a very long period of time will not corrode nor be dissolved.

Another important object of the invention is to provide a liner that can be cemented in place within the steel casing to provide a fluid seal between the liner and the casing and to take the place of any re-cementing job to shut on waters that might leak by the previously cemented casing shoe. The procedure of cementing a steel liner within a steel casing is generally not considered practical because of the great mechanical difficulties which would arise if it were necessary to remove the liner.

With the foregoing and other objects in view, which will be made manifest in the following detailed description and specifically. pointed out in the appended claims, reference is had to the accompanying drawings for an illustrative embodiment of the invention, wherein:

Figure 1 is a vertical section through an oil well illustrating the drillable liner embodying the present invention as installed therein, the liner being illustrated as being suspended from the set casing by means of a suitable liner hanger;

Fig. 2 is a vertical section through an oil well illustrating the liner installed therein, the liner being shown as supported on bottom and detaohably connected to drill pipe or tubing, this being a suitable alternative method of installing the liner; and

Figs. 3, 4, and 5 are vertical sections through oil wells illustrating the manner in which the liner embodying the present invention may be installed in another suitable manner.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, and referring rst to the disclosure made in Fig. l, designates the productive formation of the oil well abovewhich there is shown the conventional casing Il which is cemented as at I2. 'I'he liner is indicated at I3 which is made of one or more sections of tubing or pipe threadedly connected together. The

bottom ofthe liner is usually equipped with a bull nose Il, and the liner is shown as being perforated with perforations I5. The perforations I6 as shown on the drawings are somewhat exaggerated as to size. In conformity with good practice the widths of these perforations are approximately twice the average diameter of the grains which form the productive formation l0. The liner sections may be connected together such as by suitable collars, one of which is shown at I6. The upper end of the liner is connected to a suitable liner hanger shown as having expansible slips l1 which may be suitably expanded on the installation of the liner so as to engage the interior of the casing and suspend th liner therefrom.

We find it good practice to cadmium plate any steel connections or accessories for the liner, and where a liner hanger is used or other steel accessory we prefer to .cadmium plate it.

The design of the liner hanger construction forms no part of the present invention as it will be understood that any suitable liner hanger design may be employed or any other equivalent mechanism or equipment may be substituted therefor to suspend the liner in the well in such position as to extend downwardly below the bottom of the casing and into the productive zone. In Fig. 2, we have illustrated an alternative method of installing the liner wherein the productive formation is indicated at 20. The casing is indicated at 2| which is cemented as indicated at 22. The liner 23 is of the same general construction as that previously described and may be made up of one or more sections suitably perforated and threadedly connected together either by threads formed on the sections of the liner or by connecting collars. The bull nose is indicated at 24. Reference character 25 designates any preferred form of detachable or back-oil connection which connects the liner with the drill pipe indicated at 26 that may be used to position the liner or to connect the liner with tubing to which the liner is -to be ultimately connected. In this form of installation the nature of the back-oil.' connection optional and immaterial as any suitable connection between the liner and the drill pipe or tubing may be employed. However, when the connecting means is formed of steel, we prefer to cadmium plate it.

In Figs. 3, 4, and 5, the productive zone is indicated at 30 above which there is the casing 3| having a casing shoe at 32. This may or may not have been previously cemented in place. The liner forming the present invention is indicated at 33 and is suitably perforated as indicated at. 34. The bull nose is indicated at 35. Incorporated in the liner is a collar 36 which has perforations 31 radially formed therein immediately above a disc 38 which may be formed of compressed fiber or other readily drillable material. I'his disc forms a seat for a valve 39 which may be formed of one of the alloys suitable for forming the liner itself. y

wardly and outwardly extending drillable phosphorous bronze arms which resiliently expand against the walls of the well. A suitable lining which may be of canvas connects these arms thus forming a basket surrounding the liner, engaging the well walls, and forming a barrier which prevents the cement from being forced downwardly around the perforated portion of the liner. The top of the liner is provided with a suitable connector 4| which connects it to drill pipe or tubing 42. VAn inner tube 43 is threaded into the bottom of the drill pipe or tubing 42 and carries a suitable swab 44. In this method of installation it is proposed to cement the liner within the set steel casing, thus forming a seal between the liner and the casing and also cementing around the casing shoe 32 to perfect the seal around the casing in the event that the previously set oement has broken or leaks.

On lowering the apparatus into the hole, valve 39 permits upward flow of liquid into the liner preventing any collapse. When the apparatus is set, as shown in Fig. 3, cement is forced downwardly through the drill pipe 42 and is discharged from the bottom of the swab 44. The downward flow of cement closes valve 39 with the result that the cement is forced outwardly through perforations 31 into the space between the liner and the walls of the Well. Downward ow of the cement is prevented by the cement basket 40. The cement then is forced upwardly into the space between the top of the casing. The drill pipe is then unscrewed from the connector 4I and the inner tube 43 and the swab 44 are recovered and removed from the well hole, leaving the remaining apparatus as shown in Fig. 4. The cement is then allowed to set, after which drilling tools are lowered to 4drill out the cement that remains in the liner above valve 39 and to drill out the valve and the disc 38,A leaving the liner set, cemented in place as shown in Fig. 5. Sometimes, under certain conditions, the drill pipe may be unscrewed from the connector 4| prior to the discharge of the cement.

The invention primarily concerns the material which is used to form the liner and such of its associated parts as are left in the well during production and which it may be desired to subsequently remove. In the preferred embodiment of the invention the liner is composed of a heattreated alloy having the. following ingredients in approximately the following percentages:

Silicon ..percent .7 Magnesium do.. 1.25 Chromium do .25 Aluminum i Balance This alloy is drawn or extruded to form the pipe sections that compose the liner.' The preferred heat treatment consists of heating. the formed pipe sections to a temperature of between 960 F. and 980 F., after which it is quenched in cold water. If hot water is used to quench the alloy from this temperature its resistance to corrosion in the Well is considerably decreased. After having been thus heated and quenched, the pipe sections are subsequently heated and held at an elevated temperature of from 310 F. to'325 F. for a period of 18 hours and then allowed to cool. This alloy thus heat-treated has a minimum ultimate tensile strength of approximately 38,000 pounds per square inch. It is ductile and has an elongation factor of 20%.

While it is possible to use an alloy having the above ingredients in approximately the percen- Magnesium per cent 1.25 Aluminum Balance This alloy has a'n ultimate strength of approximately 29,000 pounds per square inch. It has an elongation factor of only approximately 10%. Still a further alloy that may be used has the following ingredients in approximately the following percentages:

Magnesium per cent 2.5 Chromium do .25 Aluminum Balance Such an alloy has an ultimate strength of 41,000 pounds per square inch and an elongation factor of only about 8%. It is slightly more difficult to extrude and work this material. The main objection to this material is its low elongation factor.

Another alloy that may be used has the follow- .ing ingredients in approximately the following percentages:

Silicon per cent 1.0 Magnesium do .6 Aluminum Balance This alloy has an ultimate strength of 41,000 pounds per square inch and an elongation factor of 8%. The mode of its heat treatment is the same as that above described.

For fittings or parts of the liner other than the pipe sections, an alloy that may be used consists f the following ingredients in approximately the following percentages:

Silicon per cent-- 7.0 Magnesium do .3 Aluminum Balance This alloy has an ultimate tensile strength of approximately 30,000 pounds per square inch and an elongation factor of 3%. The elongation factors mentioned herein are in two inches.

Another suitable alloy that may be used vconsists of the following ingredients in approximately the following percentages:

Magnesium 1 per cent 10 Aluminum Balance This alloy is particularly suitable for fittings or parts that are cast in shape.

Dueto its reduced ductility or flexibility the last of the above-mentioned alloys and the sili-` con-magnesium-aluminum alloy cannot 'be satisfactorily made into tubes very readily, therefore, the use of these alloys is largely confined to ilttings, accessories, and the like. The use of pure aluminum is hardly suitable for the liner or its parts for the reason that its ultimate strength is only about 13,000 pounds per square inch. It is very ductile having an elongation factor of about 45% in 'two inches but due to its greatly reduced strength it is hardly suitable for use in the liner.

The specific gravities of the above-mentioned preferred alloys run from 2.66 to 2.91.

It will be noted that all of the above-mentioned alloys consist mainly of aluminum and that those mentioned as being suitable are copper-free, containing no copper whatsoever. The forms of aluminum alloy now sold under the trade-name of Duralumin and which are most frequently used for structural purposes, contain substantial amounts of copper. The most commonly used form of Duralumin contains approximately 4% of copper. Another form of alloy sold under that name contains approximately 21/2% copper. Such alloys we find unsuitable for our purposes. We also find unsuitable for our purposes aluminum alloys containing substantial amounts of zinc. In most oil wells there are present saline solutions. The quantity of saline solution present usually increases during the production life of the well. When an aluminum alloy containing copper or zinc is subjected for a long period of time to such saline solutions as are generally encountered, the alloy slowly corrodes and dissolves. We do not propose to advance any exact explanation for this. However, as a possible theory, the presence of the copper and of the zinc in the aluminum alloy probably causes some sort of galvanic action to start up when the alloy is in these saline solutions with the result that in the course of time the liner corrodes and dissolves. Therefore, the improved liner is 'characterized by the fact that it is free of copper and it should also be free of zinc, although traces of copper or of zinc might possibly be present without any serious detrimental effect. At all events the copper content should never exceed eight tenths of one percent and it is preferable that the copper and zinc should be entirely eliminated from the composition of the liner and of its accessories.

When a. well is equipped with a liner formed of one of the materials above-described as being suitable, it may be left indefinitely in the well hole. When copper-free or zinc-free, the liner will last indeflnitely and resist corrosion under ordinary oil well conditions. If, in the course of time, it is desired to remove the liner from the well for further operations, an attempt may rst be made to pull the liner. If the liner has not become frozen or lodged in the well it has sufficient tensile strength to enable it to be removed bodily. However, as most frequently occurs, after a long period of production the liner is found to be immovably lodged in the well. In such case, the liner is drilled up by merely introducing through the casing conventional rotary drilling tools which are of the same general type as those used for drilling through the formation. The liner being comparatively soft and malleable as compared with steel, can be drilled quite readily. The usual rate of drilling is from 20 to 30 lineal feet per hour. As the specific gravity of the hner and its accessories is less than 3, the cuttings of the liner produced during the drilling may be flushed out of the well by the circulation fluid conventionally employed. Although the specific gravity of the liner cuttings is somewhat greater than the specific gravity of the conventional circulation fluid, it is suiiiciently close to it so that the velocity of the circulation uid may wash all of the cuttings entirely out of the well. The specific gravity of the liner compares favorably with the specific gravity of the ordinary well formations that are drilled through. We have `about 18 hours.

observed that fairly large cuttings or shavings willbe carried to the surface by the circulation uid and be deposited in the sump or mud ditch.

As the liner is installed in the well with the idea of at some time subsequently being forced possibly to drill it up, it is manifest that all parts of the liner, including the couplings I6, the bull noses I4, 24, and 35, the liner hanger, or the connections 25 and 4I, should be formed of one of these readily drillable, corrosion-resistant materials. By installing the liner and its fittings and accessories formed of such materials a satisfactory liner conforming 'to all recognized practices is employed. At the same time there is security in that if conditions in the Well change requiring removal of the liner, it may be removed very readily and quickly without requiring sidetracking or expensive and tedious milling operations where such milling operations are capable of being accomplished. The liner possessing the properties of ductility and flexibility is capable of giving and conforming to all normal formation shifts without danger of breaking or cracking. It also may have the perforations formed therein of the desired size with respect to the grain size of the productive formation.

Various changes may be made in the details of construction without departing from the spirit or scope of the invention as defined by the appended claims.

We claim:

1. A liner vfor use in oil wells and the like, comprising a ductile liner mainlyY composed of aluminum and which is characterized by the fact that it is substantially free of ingredients such as copper which would otherwise cause the liner to either dissolve or deteriorate in the presence of salt water or other corrosive substances frequently encountered in oil wells.

2. A liner for use in oil wells and the like, composed mainly of aluminum but containing small amounts of silicon, magnesium, and chromium.

3. A liner for use in oil wells and the like, composed mainly of aluminum but containing a small amount of magnesium.

4. A liner for use in oil wells and the like, composed mainly of aluminum but containing small amounts of magnesium and chromium.

5. A liner for use in oil wells and the like composed of the following ingredients in approximately the following proportions:

Silicon per cent-.. .7 Magnesium do 1.25 Chromium do .25 Aluminum Balance 6. A liner for use in oil wells and the like composed of the following ingredients in approximately the following proportions: Y

Silicon per cent-- .7 Magnesium do 1.25 Chromium do .25 Aluminum Silicon per cent .7 Magnesium ..do 1.25 Chromium ..-do .25 Aluminium...y Balance and heat treated by heating to 960 to 980 F., and then quenching in cold water and then maintaining it at a temperature of 310 to 325 F. for

8. 'Ihe method of placing oil wells on production which includes the step of positioning in the well so as to extend downwardly below the botfom of the casing a ductile liner composed mainly of aluminum and which is readily drillable and which has a specific gravity of less than 3 and which is characterized by being substantially free of copper so as to be corrosion-resistant whereby if conditions of the well change requiring removal of the liner, the liner may be drilled up by conventional well drilling equipment and the cuttings ushed out by the circulation fluid.

9. A liner ior use in oil wells and the like, comprising a liner composed mainly of aluminum and having a low specific gravity and which has less than .8% of copper.

10. A liner for use in oil wells and the like, which is composed mainly of aluminum and which is ductile having an ultimate tensile strength in excess of 29,000 pounds per square inch.

11. A liner for use; in oil wells and the like which is formed mainly of aluminum having a specic gravity of less than 3 and an elongation factor of in excess of 8%.

12. A liner for use in oil wells and the like which isAformed of an alloy of aluminum composed mainly of aluminum having a specific gravity of less than three and which is characterized by being zinc free and if containing any copper contains less than .8%.

13. A liner for use in oil wells and the like which is formed of an alloy of aluminum coinposed mainlyv of aluminum having a. specific gravity of less than three and which is characterized by being zinc free and if containing any copper contains less than .8%, said liner also being characterized by the fact that it is heat treated so as to have a tensile strength in excess of 29.000 pounds per square inch.

ELWIN B. HALL.

Aamnnnammu'mou'r. 

